experimental investi gation of heat transfer ......8.73% at 0.02% concentration when compared to...
TRANSCRIPT
International Journal of Mechanical Engineering and Technology (IJMET)Volume 8, Issue 8, August 2017, pp.
Available online at http://www.iaeme.com/IJME
ISSN Print: 0976-6340 and ISSN Online: 0976
© IAEME Publication Scopus
EXPERIMENTAL INVESTI
TRANSFER COEFFI
FACTOR IN A DOUBLE P
EXCHANGER WITH AND W
TAPE INSERTS
GLYCOL
Dept. of Mechanical Engineering
Dept. of Mechanical Engineering
ABSTRACT
Heat transfer coefficient and friction factor of ZnO Nanofluid passing in the
double pipe heat exchanger with and without twisted tapes along with wire coil are
placed in the experimental investigation. The ratio of the base fluids are 60:40 water
and Propylene glycol are considered. The volume concentrations of ZnO Nanofluid
0.15, 0.25, and 0.4 % are taken. The double pipe heat exchanger has an inner tube in
which different twisted tape configurations are inserted, the twist ratios are 10, 5, and
3 are taken. The flow rates are taken for cold and hot water, the ranging of cold and
hot water are 0.083 to 0.3116 and 0.1466 Kg/Sec are taken in the experimental study.
The results shows that the Nusselt number for double pipe heat exchanger was
increased at 0.4% concentration of ZnO Nanofluid with twisted tape at the ratio of
H/D= 3 the heat transfer enhanced by 23.56% and the friction factor was increased
by 15.32% compared with the base fluid. The Reynolds number ranging from 3000 to
8000. The error ranging of �Keywords: Double pipe heat exchanger, Heat transfer, Friction
Twisted tape, Wire coil.
Cite this Article: T. Vijaya sagar,
heat transfer coefficient and friction factor in a double pipe heat exchanger with and
without twisted tape inserts using zno
Journal of Mechanical Engineering and Technology
http://www.iaeme.com/IJMET/issues.
International Journal of Mechanical Engineering and Technology (IJMET) 2017, pp. 94–106, Article ID: IJMET_08_08_012
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=8
6340 and ISSN Online: 0976-6359
Scopus Indexed
EXPERIMENTAL INVESTIGATION OF HEAT
TRANSFER COEFFICIENT AND FRICTION
FACTOR IN A DOUBLE PIPE HEAT
EXCHANGER WITH AND WITHOUT TWISTED
INSERTS USING ZNO-PROPLYENE
GLYCOL NANO FLUID
T. Vijaya sagar
Dept. of Mechanical Engineering K L University Guntur,
Andhra Pradesh, India
Dr.Y.Appalanaidu
Dept. of Mechanical Engineering K L University Guntur,
Andhra Pradesh, India
Heat transfer coefficient and friction factor of ZnO Nanofluid passing in the
double pipe heat exchanger with and without twisted tapes along with wire coil are
placed in the experimental investigation. The ratio of the base fluids are 60:40 water
ylene glycol are considered. The volume concentrations of ZnO Nanofluid
0.15, 0.25, and 0.4 % are taken. The double pipe heat exchanger has an inner tube in
which different twisted tape configurations are inserted, the twist ratios are 10, 5, and
en. The flow rates are taken for cold and hot water, the ranging of cold and
hot water are 0.083 to 0.3116 and 0.1466 Kg/Sec are taken in the experimental study.
The results shows that the Nusselt number for double pipe heat exchanger was
concentration of ZnO Nanofluid with twisted tape at the ratio of
H/D= 3 the heat transfer enhanced by 23.56% and the friction factor was increased
by 15.32% compared with the base fluid. The Reynolds number ranging from 3000 to � 5 of the experiment.
Double pipe heat exchanger, Heat transfer, Friction factor, Nanofluid,
T. Vijaya sagar, Dr.Y.Appalanaidu, Experimental investigation of
heat transfer coefficient and friction factor in a double pipe heat exchanger with and
without twisted tape inserts using zno-proplyene glycol nanofluid, International
Journal of Mechanical Engineering and Technology 8(8), 2017, pp. 94–106.
T/issues.asp?JType=IJMET&VType=8&IType=8
T&VType=8&IType=8
GATION OF HEAT
CIENT AND FRICTION
IPE HEAT
TWISTED
PROPLYENE
Heat transfer coefficient and friction factor of ZnO Nanofluid passing in the
double pipe heat exchanger with and without twisted tapes along with wire coil are
placed in the experimental investigation. The ratio of the base fluids are 60:40 water
ylene glycol are considered. The volume concentrations of ZnO Nanofluid
0.15, 0.25, and 0.4 % are taken. The double pipe heat exchanger has an inner tube in
which different twisted tape configurations are inserted, the twist ratios are 10, 5, and
en. The flow rates are taken for cold and hot water, the ranging of cold and
hot water are 0.083 to 0.3116 and 0.1466 Kg/Sec are taken in the experimental study.
The results shows that the Nusselt number for double pipe heat exchanger was
concentration of ZnO Nanofluid with twisted tape at the ratio of
H/D= 3 the heat transfer enhanced by 23.56% and the friction factor was increased
by 15.32% compared with the base fluid. The Reynolds number ranging from 3000 to
factor, Nanofluid,
Experimental investigation of
heat transfer coefficient and friction factor in a double pipe heat exchanger with and
International
T. Vijaya Sagar,Dr.Y.Appalanaidu
http://www.iaeme.com/IJMET/index.asp 95 [email protected]
1. INTRODUCTION
Heat exchangers are the equipment that is commonly used to transfer heat between two
passing fluids at different temperatures without any mixing of fluids with each other. Transfer
of energy from one fluid to another fluid can be done modes of heat transfer. Heat exchangers
with the convective heat transfer of fluid inside the tubes are frequently used in the many
engineering applications like heavy industries, power plants, automotive, chemical industries,
metallurgical, electronics components, refrigeration’s, air conditions and duct systems.
Enhancement of heat transfer intensity in all types of thermo technical apparatus is of very
important for industries. For the savings of power generations, it also leads to a moderating in
size and weight. Up to the present work, several heat transfer enhancement techniques have
been developed. Twisted tapes is one of the most important element of enhancement
techniques. The combination of water and propylene glycol are being used as the coolant due
to advantages of new technologies there are a number of improvements in the field
engineering applications including the enhancement of heat transfer capabilities. Tubes with
rough surfaces have much higher heat transfer coefficients than tubes with smooth surfaces.
Therefore, tubes surfaces are often intentionally roughened, corrugated, or finned in order to
enhance the convection heat transfer coefficient and thus the convection heat transfer rate.
Turbulence flow in tube the heat transfer has been increased as much 40% by roughening the
surface. Among many techniques investigated for augmentation of heat transfer rates inside
circular tubes, a wide span of inserts has been utilized, specifically, when turbulence flow is
considered.
The inserts investigated that included coil wire inserts, brush inserts, mesh inserts, strips
inserts, twisted tapes inserts etc. Augmentation of convective heat transfer in internal flow
with tape placed in tubes is a well approved technique hire in industrial particles. The present
investigation is aimed at studying the frictional and heat transfer characteristics in turbulent
region using varying width twisted tape with coil spring placed under constant will heat flux.
The objective of using varying width twisted tapes is to minimize the pressure drops
associated with full width twisted tapes without seriously impairing the heat transfer
augmentation rates and to achieve material ranges .However, due to micron size of particles
there were several problems like sedimentation and erosion of tubes and pumps while in
transmit. In the resent past the availability of Nano material’s renewed the interest in the
application of Nanofluids. The suitability and performance of the conventional fluids can be
enhanced by introducing Nano particles like Al2O3, TiO2, ZnO and CuO, by converting them
in to Nanofluids.
[1] Chandra Sekhara teddy: The experimental carried out by heat transfer coefficient
and friction factor for Tio2 Nanofluid passing in a double pipe heat exchanger with and
without heical coil placed are experimentally studied. The volume concentrations are
0.0004% to 0.02% of Nanofluid are taken and the based fluid ratio are 60:40 for water and
ethylene glycol. The heat transfer coefficient and friction factor are enhanced by 10.83% and
8.73% at 0.02% concentration when compared to base fluid without helical coil. Heat transfer
coefficient and friction factor further get enhanced by 13.85% and 10.69% respectively for
0.02% concentration Nanofluid when compared to base fluid flowing in a tube with helical
coil placed P/d = 2.5.
[2] P.V.Durga Prasad and Gupta: The experimental carried out by investigation on heat
transfer enhancement on U-bend heat exchanger and twisted tape using water Al2O3
Nanofluid. The volume concentration of Nanofluid are 0.01% and 0.03% are taken. Twist
ratio for twisted tapes are ranging between 5 and 20. The results showed that the Nusselt
number of entire pipes for 0.03% concentration of Nanofluid with twisted tapes placed is
Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid
http://www.iaeme.com/IJMET/index.asp 96 [email protected]
enhanced by 31.28% compared to the water. The friction factor increased by 1.23 times
compared with the water while placing the twisted tapes H/D = 5.
[3] Hasanpour, Farhadi and Sedighi: The experimental carried out by which has inner
tube filled with various categories of twisted tapes. From conventional to modified types
which includes perforated V-cut and U-cut types. The twist ratios are 3, 5 and 7 and the
Reynolds number range from 5000 to 15000. The results showed that the Nusselt number and
friction factor for all cases of twisted tapes corrugated tube are more than the empty
corrugated tube.
[4] V. Chandraprabu and Sankaranarayanan: The experimental carried out by heat
transfer performance of Nanofluid Al2O3 water and CuO water is expressed by using the
condensing unit of an air conditioner. The volume concentrations of Nanofluid are 1, 2, 3, and
4. Two nanofluids shows better heat transfer rate than does the base fluid. The Cuo water
Nanofluids better heat transfer rate than Al2O3 water Nanofluids.
[5] P.V.Durga Prasad and gupta: In this study the volume concentrations of Al2O3
Nanofluid are 0 to 0.03%, and longitudinal strip placed of aspect ratios are 1, 2, 4, and 12 are
taken. The results shows that the Nusselt number and friction factor of entire pipes for 0.03%
concentration of Nanofluid with longitudinal strip placed ratio of 1 enhances by 47.35% and
1.21 times compared with base fluid.
[6] Hamid and Mohammadiun: In this study of Al2O3/ethylene glycol (EG) are taken,
The three different volume concentrations of Al2O3 Nanofluid are 0.5, 1, and 1.5% and at
three different twist ratios of twist tapes y/w = 2, 3.6 and 5 are taken. The results shows that
utilization of twists together with Nanofluid tends to increase the heat transfer and friction
factor, the thermal performances factor 4.2 is found with the use of Al2O3/EG Nanofluid at
concentration at 0.5% by volume is corrugated tube together with twisted tape at twist ratio 2.
[7] Kushalkamboj and rohitsharma: In this study experimentally investigated the heat
transfer augmentation by means of divergent-convergent spring coil turbulent and tried to find
the optimum pitch which augmentation heat transfer is maximum. The pitch ratios are 5, 10
and 15cm. The Nusselt number enhanced by 26.76% and maximum friction factor is 66.87%
at pitch ratio=5cm, thermalperformance factor maximum is 1.0525 at pitch ratio=15.
[8] SarmadA.Abdal Hussein: Experimentally Investigation of heat transfer and friction
factor of double pipe heat exchanger, inserted semi circular disc baffles with spacing of 15cm
and 45cm carriedout for turbulent flow. The semi circular disc baffles 15 and 45cm the heat
transfer rate by 1.9 and 1.3 times of smooth tube are placed. The results shows that the
inserted tape with 15cm has maximum friction factor than that with 45cm and the
experimental data with average error of �7.8%for nusselt number and �6.5%for friction
factor.
[9] Anil Singh Yadav: Investigation on double pipe heat exchanger with and without
twisted tapes at different mass flow rate. As compared to conventional heat exchanger, the
augmented has heat exchanger has shown a significant improvement in heat transfer
coefficient by 40% for half-length twisted tape. At the equal mass flow rate heat transfer
performance of half-length twisted tape is maximum compared to smooth tube. The results
shows that on unit pressure drop basis the heat transfer performance of smooth tube is
maximum compared to twisted tape, thermal performance of smooth tube is better than half-
length twisted tape by 1.3-1.5 times.
[10] Madhav Mishra and Nayak: Experimentally investigation of effectiveness and
overall heat transfer coefficient of double pipe heat exchanger. Triangular baffles of 100mm
and 50mm pitches enhance the average effectiveness by 1.42 and 1.62 times in parallel flow
T. Vijaya Sagar,Dr.Y.Appalanaidu
http://www.iaeme.com/IJMET/index.asp 97 [email protected]
and in counter flow are 1.338 and 1.62. The average heat transfer rate are 1.6 and 1.9 times in
parallel flow and in counter flow are 1.48 and 1.67 that of smooth tube respectively.
[11] Swathi and Kishore: Experimentally investigation of effectiveness in double pipe
heat exchanger, setup-1 rectangular fins and twisted tapes insert inside pipe, setup-2 only
twisted tapes without fins insert outside pipe. Effectiveness is higher for setup-1 heat
exchanger then setup-2 heat exchanger. LMTD and Turbulence increased for setup-1 heat
exchanger than setup-2 heat exchanger. So by using fins in addition to twisted tapes
effectiveness can be enhanced.
[12] Amar Raj and Sing Suri: Multiple square perforated with square wing twisted tape,
the width ratio is wd/wt 0.042 to 0.167. The results showed that the maximum value
increases at 6.96 and 8.34 times nusselt number and friction factor at depth ratio of 0.167 with
compare to plain tube.
[13] BehroutRaei: fully developed turbulence slow heat transfer and the pressure drop
behavior of Al2O3/ water. The volume concentrations of nanofluids are 0.05 to 0,15 are taken.
The results shows enhancement of heat transfer and friction factor are 23 and 25% at 0.15
volume concentration compare with base fluid.
[14] K.M. Elshazly: Thermal performance of shell and coil heat exchanger with different
ferent coil torsions. Five helical coil tubes ranging between 0.0442< and > 0.1348 are taken.
The volume concentration of nanofluid are 0 to 2% are taken. The results shows that reduces
the coil torsion and enhance heat transfer rate of Nanofluid.
[15] Byung-Hee chen: Alumin Nanofluid and transformer oil of which flow through
double pipe heat exchanger system in the laminar flow enhances the heat transfer coefficient.
At highest concentration the heat transfer rate is increases.
The data on the mixture of propylene glycol and water based Nanofluid passing in a tube
with inserts twisted tapes with coil springs is not available in the literature. Therefore, the
focus of the present work is on the estimation heat transfer coefficient and friction factor of
propylene glycol and water mixture based on ZnO Nanofluid passing in double pipe heat
exchanger with twisted tapes with coil spring are placed in investigation. The experiments on
heat transfer are conducted by the Reynolds number range from 3000 to 8000. Based on the
experimental data generalized correlations are proposed for Nusselt number and friction
factor.
2. PREPARATION OF ZNO NANOFLUID
Preparation of Nanofluids is one of the key tasks for enhancing the heat transfer by using
nanofluids in many applications .particle agglomeration and particles dispersion in base fluid
are two key factors to look upon for preparing a stable nanofluid , particle agglomeration
leads to increase in particle size and particles should be well dispersed so that there will be no
settlement in the base fluid and generally there are two methods for preparation of one step
method and two step method. The Zno (Zinc oxide) nano particles used in this study were
purchased from Sigma-Aldrich having 50nm nearly spherical particles. The two step method
is used for preparing the nanofluid .the base fluid used in this experiment is water -propylene
glycol mixture (60:40). Firstly, the nano particles are dissolved in the base fluid and of
20litres and constantly stirred for 45 min and for eliminating the agglomeration and for the
proper dispersion of the nano particles the fluid is sonicated for 2h.the nano fluids are
prepared in three different concentrations (i.e. 0.15%, 0.25% and 0.4%) the amount of
particles required for each concentration is calculated by:
Experimental investigation of heat
exchanger with and without twisted tape inserts using zno
∅
ρ��C���
A) Thermal conductivity of Nanofluid:
Thermal conductivity is one of the important parameter which has a impact on the heat
transfer enhancement .the effective thermal conductivity of Nanofluid is measured by KD2
PRO thermal property meter .which is done by probe (Read time
for Nanofluid and base fluid are measured at different temperatures to predict the Thermal
conductivity of Nanofluids is calculated using the following equation given by Hamilton and
Crosser:
���In the above equations ∅ , p ,
and density subscripts basefluid and Nanofluid refer to the base fluid and Nanofluid
respectively. z is the empirical shape factor as the Nano particles used in this investigation
are nearly spherical z is taken as 3 cp is the specific heat.
Figure 1 represents the comparison between the ratio of thermal conductivity of Nanofluid
to the base fluid and the double pipe heat exchanger inlet temperatures from the literature
thermal conductivity of Nano fluid found to be increasing with increase in temperature and
Nano particle volume concentration. in the above graph the two trends depicts the measured k
value of 0.4% ∅ nanofluid and theoretical values of k obtained from hamilton
Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat
exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid
∅ � � ������������������������������������������ ����� ! " 100 (1)
�� � ∅ρ% & '1 ( ∅)ρ*� (2)
�� � '1 ( ∅) +�,-�.-/C�*� & ∅+�0�.-/ C%� (3)
Thermal conductivity of Nanofluid:
Thermal conductivity is one of the important parameter which has a impact on the heat
ment .the effective thermal conductivity of Nanofluid is measured by KD2
PRO thermal property meter .which is done by probe (Read time- 60 Seconds).the values of k
for Nanofluid and base fluid are measured at different temperatures to predict the Thermal
onductivity of Nanofluids is calculated using the following equation given by Hamilton and
�� � 1��'234)15�3∅'234)'15�31�)1��'234)15�3∅'15�31�) �6� (4)
, p ,7 ,8 refer to the volumetric concentration ,particle, viscosity
and density subscripts basefluid and Nanofluid refer to the base fluid and Nanofluid
respectively. z is the empirical shape factor as the Nano particles used in this investigation
erical z is taken as 3 cp is the specific heat.
Figure 1
represents the comparison between the ratio of thermal conductivity of Nanofluid
to the base fluid and the double pipe heat exchanger inlet temperatures from the literature
ivity of Nano fluid found to be increasing with increase in temperature and
Nano particle volume concentration. in the above graph the two trends depicts the measured k
nanofluid and theoretical values of k obtained from hamilton-crosser
transfer coefficient and friction factor in a double pipe heat proplyene glycol nanofluid
Thermal conductivity is one of the important parameter which has a impact on the heat
ment .the effective thermal conductivity of Nanofluid is measured by KD2
60 Seconds).the values of k
for Nanofluid and base fluid are measured at different temperatures to predict the Thermal
onductivity of Nanofluids is calculated using the following equation given by Hamilton and
refer to the volumetric concentration ,particle, viscosity
and density subscripts basefluid and Nanofluid refer to the base fluid and Nanofluid
respectively. z is the empirical shape factor as the Nano particles used in this investigation
represents the comparison between the ratio of thermal conductivity of Nanofluid
to the base fluid and the double pipe heat exchanger inlet temperatures from the literature
ivity of Nano fluid found to be increasing with increase in temperature and
Nano particle volume concentration. in the above graph the two trends depicts the measured k
crosser model
T. Vijaya Sagar,Dr.Y.Appalanaidu
.the measured values are much higher than the prediction . probably because these classical
models do not account for the parameters like particle size, Brownian motion and Nano
layering .which are important to consider in Nanofluids.
B) Viscosity of Nanofluid :
The viscosity of the Nano fluid is measured by using the rotary viscometer
(BROOKFIELD) .the reading were taken at different concentrations an
Nano fluid. The viscosity of the Nano fluid increases with increase in the particl
concentration and decreases with the increase in temperature. is observed from the
measurements and the literature as well
Figure 2 represents the comparison between the viscosity and the fluid inlet temperatures
of the double pipe heat exchanger temperature is an important parameter to consider for
viscosity of Nanofluids. The viscosity of the Nanofluids decreased with increased in
temperature. The graph depicts that the Nanofluid of highest concentration i.e., 0.4% at lowest
temperature shows highest value of viscosity and vice versa.
3. EXPERIMENTAL SETUP
The experimental unit consists of flow meters, thermocouple, u tube manometer data logger,
receiving tanks(hot, cold) induction motor of 0.5 Hp capacity .The test section consists of
concentric pipes and u bend made of stainless steel inner diameter of inner tube is 0.019
length of test section is 2m,u bend radius of 0.32
small compared to surface of concentric pipes so heat transfer in bend region can be
neglected. Two motors of 0.5Hp capacity are used to pump the Nanofluid and
hot fluid is pumped through the annulus of the concentric tube and Nanofluid flows through
inner tube. Flow meter of maximum 0.3116 kg/sec are used to control the flow rates and
throughout the experiment mass flow rate of hot water is kept
flow rates of Nanofluid is varied from 0.0833 to 0.3116 Kg/sec. The surface area related to
bend region is relatively small compared to areas of inner and outer tubes. In order to measure
the temperature a total of four (4) therm
in the inlet and outlets of pipes.
T. Vijaya Sagar,Dr.Y.Appalanaidu
.the measured values are much higher than the prediction . probably because these classical
models do not account for the parameters like particle size, Brownian motion and Nano
layering .which are important to consider in Nanofluids.
The viscosity of the Nano fluid is measured by using the rotary viscometer
(BROOKFIELD) .the reading were taken at different concentrations and temperatures of
he viscosity of the Nano fluid increases with increase in the particl
concentration and decreases with the increase in temperature. is observed from the
ents and the literature as well.
Figure 2
represents the comparison between the viscosity and the fluid inlet temperatures
of the double pipe heat exchanger temperature is an important parameter to consider for
he viscosity of the Nanofluids decreased with increased in
temperature. The graph depicts that the Nanofluid of highest concentration i.e., 0.4% at lowest
temperature shows highest value of viscosity and vice versa.
EXPERIMENTAL SETUP
unit consists of flow meters, thermocouple, u tube manometer data logger,
receiving tanks(hot, cold) induction motor of 0.5 Hp capacity .The test section consists of
concentric pipes and u bend made of stainless steel inner diameter of inner tube is 0.019
m,u bend radius of 0.32m. As surface area related to bend is very
small compared to surface of concentric pipes so heat transfer in bend region can be
neglected. Two motors of 0.5Hp capacity are used to pump the Nanofluid and hot Fluid, The
hot fluid is pumped through the annulus of the concentric tube and Nanofluid flows through
inner tube. Flow meter of maximum 0.3116 kg/sec are used to control the flow rates and
throughout the experiment mass flow rate of hot water is kept constant 0.1416 kg/sec and
flow rates of Nanofluid is varied from 0.0833 to 0.3116 Kg/sec. The surface area related to
bend region is relatively small compared to areas of inner and outer tubes. In order to measure
the temperature a total of four (4) thermocouple are used and thermocouple needles are placed
.the measured values are much higher than the prediction . probably because these classical
models do not account for the parameters like particle size, Brownian motion and Nano
The viscosity of the Nano fluid is measured by using the rotary viscometer
d temperatures of
he viscosity of the Nano fluid increases with increase in the particle
concentration and decreases with the increase in temperature. is observed from the
represents the comparison between the viscosity and the fluid inlet temperatures
of the double pipe heat exchanger temperature is an important parameter to consider for the
he viscosity of the Nanofluids decreased with increased in
temperature. The graph depicts that the Nanofluid of highest concentration i.e., 0.4% at lowest
unit consists of flow meters, thermocouple, u tube manometer data logger,
receiving tanks(hot, cold) induction motor of 0.5 Hp capacity .The test section consists of
concentric pipes and u bend made of stainless steel inner diameter of inner tube is 0.019 cm
m. As surface area related to bend is very
small compared to surface of concentric pipes so heat transfer in bend region can be
hot Fluid, The
hot fluid is pumped through the annulus of the concentric tube and Nanofluid flows through
inner tube. Flow meter of maximum 0.3116 kg/sec are used to control the flow rates and
constant 0.1416 kg/sec and
flow rates of Nanofluid is varied from 0.0833 to 0.3116 Kg/sec. The surface area related to
bend region is relatively small compared to areas of inner and outer tubes. In order to measure
ocouple are used and thermocouple needles are placed
Experimental investigation of heat
exchanger with and without twisted tape inserts using zno
① Hot water Tank③ Induction Motors 0.5Hp⑤ U-Tube manometer ⑦ Coil Heaters
ZnO Nano fluid flow
The thermocouple readings are recorded by using multi point digital temperature
indicator. In order to minimize the heat loss from the system to atmosphere it is insulated the
outer surface of annulus tube is wounded with asbestos rop
Nanofluid and hot water are of 20 ltrs capacity made of stainless steel. Pressure drop across
Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat
exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid
Figure 3
Hot water Tank ② ZnO Nano fluid Tank
Induction Motors 0.5Hp ④ Flow control valves
Tube manometer ⑥ Flow meter
ZnO Nano fluid flow Hot water flow
Figure 3 (a) [H/D=3]
Figure 3 (b) [H/D=5]
Figure 3 (c) [H/D=10]
The thermocouple readings are recorded by using multi point digital temperature
indicator. In order to minimize the heat loss from the system to atmosphere it is insulated the
outer surface of annulus tube is wounded with asbestos rope. The tank capacities of both
Nanofluid and hot water are of 20 ltrs capacity made of stainless steel. Pressure drop across
transfer coefficient and friction factor in a double pipe heat proplyene glycol nanofluid
Tank
The thermocouple readings are recorded by using multi point digital temperature
indicator. In order to minimize the heat loss from the system to atmosphere it is insulated the
e. The tank capacities of both
Nanofluid and hot water are of 20 ltrs capacity made of stainless steel. Pressure drop across
T. Vijaya Sagar,Dr.Y.Appalanaidu
http://www.iaeme.com/IJMET/index.asp 101 [email protected]
the inner tube of test section is calculated by a u tube manometer with mercury as a
Manometric fluid. The tubes in the test section were cleaned with distilled water prior to using
Nanofluid. The Thermo physical properties of the Nanofluid are estimated at bulk mean
temperature. Primary purpose of the work is to place twisted tape with wire coils in the inner
tube of the test section and this passive augmentation technique is to generate a swirl /
turbulent flow and they obstruct the flow leading to more fluid mixing for high heat transfer
enhancement. Three variations of Twist Ratios are shown in figure 3 (a),3(b),3(c) and spring
pitch was kept constant for all twisted tape configurations.
4. THEORETICAL ANALYSIS
Data reduction
Measurement of Heat transfer coefficient:
The heat transfer coefficient for hot fluid as follows as:
@A � BA∁DA∆F � BA∁DA'FAG ( FAH) (5)
Where Qh is the heat transfer coefficient at hot fluid, mh is the mass flow rate at hot fluid,
Cph is the specific heat at hot fluid and Thi and Tho are the inlet and outlet temperatures at hot
fluid.
The heat coefficient for cold fluid follows as:
@I � BI∁DI'FIH ( FIG) (6)
Where Qc is the heat transfer coefficient at cold fluid, mc is the mass flow rate at cold
fluid, Cpc is the specific heat at cold fluid and Tci and Tco are the inlet and outlet temperatures
at cold fluid.
The average heat transfer coefficient follows as:
@JKL � MN�M�O (7)
Where Qavg is the average heat transfer coefficient, Qh is the heat transfer at hot fluid and
Qc is the heat transfer coefficient at cold fluid.
The temperature difference at LMTD follows as:
∆FPQRS � 'RN�3R��)3'RNT3R�T)U�VWN�XW�TWNTXW��Y (8)
Where ∆FPQRS is the temperature difference at LMTD, Thi is the hot inlet temperature, Tci
is the cold inlet temperature, Tho is the hot outlet temperature and Tco is the cold outlet
temperature.
The Nusselt number follows as:
Z[\]D^ A_`�"S1 (9)
Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid
Where NuExp is the Nusselt number at experimental, hexp is the heat transfer rate, D is the
diameter and k is the thermal conductivity.
4A� � 4a�3b�c�d�� (10)
eG � Mfghij"∆RklWm (11)
nG � opGL (12)
The heat transfer rate is given follow as:
q\]D � M�gh∆RklWm"ij (13)
Where hexpis the experimental heat transfer rate, Qavg is the average heat transfer
coefficient, ∆FPQRS is the difference in temperature and Ai is the area at inner side.
rs � tuvNw (14)
'Z[)S.x = 0.023 × rs{.|}~{.� (15)
Where Nu is the Nusselt number, Re is the Reynolds number and Pr is the Prandlt number.
Measurement of friction factor:
�s]D = ∆�+km/V
���� Y
(16)
�x�J�G�� = 0.3164 × r�3{.O� (17)
Where fexp is the experimental friction factor,∆P is the mean pressure, L is the length, D is
the diameter, 8 is the density, V is the volume and Re is the Reynolds number.
5. RESULTS AND DISCUSSIONS:
a) Base Fluid data:
The setup is validated before conducting experiment by using base fluid Distilled water and
propylene glycol (60:40) ratio. and the results were plotted for Nusselt number and friction
factor with equation number 15 of Dittus- Boelter and equation number 17 Blasius .the
difference between experimental and theoretical data were found to be 5% for Nusselt
number and 8% for friction factor as shown in figure 4 and figure 5.
Figure 4
050
100150
0 2000 4000 6000 8000
Nu
sse
lt N
um
be
r, N
u
Renolds Number Re
Nu D- B
Nu Exp
T. Vijaya Sagar,Dr.Y.Appalanaidu
b) Base Fluid with twisted tape configuration:
Now the experiment is conducted with base
Compared to the plain tube the Nusselt number and friction factor is more for twist ratio
configuration H/D=3. The data obtained is shown in
0
0.01
0.02
0.03
0.04
0.05
0.06
0Fri
ctio
n f
act
or
f
0.00
0.02
0.04
0.06
0
Fri
ctio
n f
act
or
f
T. Vijaya Sagar,Dr.Y.Appalanaidu
Figure 5
Base Fluid with twisted tape configuration:
t is conducted with base fluid on different twisted tape configurations.
Compared to the plain tube the Nusselt number and friction factor is more for twist ratio
configuration H/D=3. The data obtained is shown in figure 6 and figure 7.
Figure 6
Figure 7
2000 4000 6000 8000
Renolds Number Re
nu
nu exp
2000 4000 6000 8000
Renolds Number Re
f Exp
f 10 TT
f 5 TT
f 3 TT
fluid on different twisted tape configurations.
Compared to the plain tube the Nusselt number and friction factor is more for twist ratio
Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid
c) ZnONano Fluid data:
Figure 9
Now the experiment is conducted with ZnO Nanofluid of 0.15, 0.25, 0.40 % volume
concentrations in a tube and the Nu values are estimated from equation 9 and shown in figure.
From the graph it is known that for ZnO Nanofluid 0.4% volume concentration the Nusselt
number enhancement is 13.7% and 19.72% within Reynolds number of 3000 and 8000 as
shown in figure 8. another graphical plot of frictional factor for the same volume
concentrations is shown in figure 9 . There was a pressure drop across the test section and it
was compared to the base fluid for 0.4% volume concentration it is increased by 9.72% and
11.48% with Reynolds number ranging between 3000 and 8000. Figure 8
d) ZnONano Fluid with twisted tape configuration:
From figure 10 the experimental data for Zno Nanofluid 0.4% volume concentration the
Nusselt number enhancement obtained were 14.1% & 20.96% at twisted tape configuration
H/D=10 and for H/D=3 the Nusselt number enhancement obtained were 15.21% & 23.56%
with Reynolds number between 3000 and 8000. It is observed from data that Nusselt number
at twisted tape configuration H/D=3 exhibits higher values. By introducing the twisted tape
configuration it produces swirl / turbulent flow in the tube which gives higher fluid mixing, so
higher the convective heat transfer. Further friction factor analysis for the ZnO Nanofluid of
0.4% and 0.15% volume concentration with different twisted tape configurations are obtained
were more compared to base fluid as shown in figure 11. observations from figure 11 are for
0.4% volume concentration and twisted tape configuration H/D=3 friction factor enhancement
at Reynolds number 3000 is 12.16% and at Reynolds number 8000 is 15.32% that of base
fluid. It was found that friction factor decreases with increase in Reynolds number and
volume concentration, and decreases with Twist ratio.
Figure 10
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0 2000 4000 6000 8000
fric
tio
n f
act
or
f
Reynolds number Re
f base fluid
f 0.15%
f 0.25%
f 0.4%
0
20
40
60
80
100
120
140
160
0 1000 2000 3000 4000 5000 6000 7000 8000Nu
sse
lt N
um
be
r N
u
Renolds Number Re
Nu 0.15% H/D=15
Nu 0.15% H/D=10
Nu 0.15% H/D=5
Nu 0.25% H/D=15
Nu 0.25% H/D=10
Nu 0.25% H/D=5
Nu 0.4% H/D=15
T. Vijaya Sagar,Dr.Y.Appalanaidu
Figure 11
6. CONCLUSION
The experimental results of the heat transfer enhancement by using ZnO nanofluid in a double
pipe heat exchanger fitted twisted tape with wire coil inserts leads to following conclusions.
• Compared to the base fluid in a tube and 0.4% volume concentration of nanofluid in a
tube with twisted tape configuration of H/D=3 the Nusselt number improvement is
15.21% and 23.56% with in the Reynolds number of 3000 and 8000.
• The friction factor of 0.4% Zno nanofluid flowing in a tube with twisted tape
configuration of H/D=3 increases 12.16% at a Reynolds number of 3000 and 15.32%
increase at a Reynolds number of 8000 compared to identical concentration fluid
without twisted tape inserts.
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0
0.01
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